Fuel-injection pump

ABSTRACT

A fuel-injection pump of the distributor type has a distributor shaft which is coupled fixedly in terms of rotation to a drive shaft and which, during rotation, successively supplies an injection nozzle with fuel from a pump working space. Seated displaceably in each case in one of a plurality of radial bores in the distributor shaft are pump pistons which, on the one hand, limit the pump working space and, on the other hand, bear non-positively on a coaxial cam ring via rollers held in roller shoes. For a construction of the injection pump which is advantageous in manufacturing terms, the drive shaft engages over the distributor shaft by means of a cup-like coupling head, and a number corresponding to the number of radial bores, of axial slots for the displaceable reception of the roller shoes are made in the cup wall. The coupling takes place via a coupling disk which is seated positively in the axial slots by means of radially projecting coupling webs and which positively receives in a recess an end projection on the distributor shaft.

STATE OF THE ART

The invention is directed to a fuel-injection pump as set forthhereinafter.

In a known fuel-injection pump of this so-called distributor type withradial pistons (EP 0,244,340 B1 or EP 0,303,237 A2), the distributorshaft carries, in the region of the radial bores receiving the pumppistons, a shaft portion of substantially larger diameter, in whichradial indentations are made in line with the radial bores receiving theradial pistons, in which indentations the roller shoes together with therollers or cylinders rotatably held therein are inserted displaceably.The coupling of the distributor shaft and drive shaft takes place viapairs of claws which project on the end faces of the distributor shaftand drive shaft and which engage without play in one another.

This constructive design necessitates a high manufacturing outlay forproducing the distributor shaft and the cam mechanism, thus resulting inhigh manufacturing costs.

ADVANTAGES OF THE INVENTION

An advantage of the fuel-injection pump is that, by shifting the rollershoes together with the rollers into the drive shaft rotatingsynchronously with the distributor shaft, the distributor shaft can beproduced substantially more simply as a lathe-turned part, and that, byinserting the roller shoes together with the rollers into simple axialslots in the hollow-cylindrical drive-shaft coupling head engaging overthe distributor shaft on its end face, the drive shaft too can bemanufactured cost-effectively; for in contrast to recesses orindentations to be countersunk radially in solid bodies of revolution,axial passage slots can be produced in hollow-cylindrical bodies ofrevolution very much more simply and cost-effectively in manufacturingterms.

Advantageous developments and improvements of the fuel-injection pumpspecified in herein are possible as a result of the measures listedhereinafter.

In a preferred embodiment of the invention, the rotationally fixedcoupling between the drive shaft and distributor shaft is brought aboutby a coupling disk which is seated in the axial slots in the couplinghead by means of coupling webs projecting radially on the diskcircumference and preferably in one piece with said disk and whichpositively receives in a central recess a projection on the end face ofthe distributor shaft.

For a positive connection between the radial coupling webs of thecoupling disk and the axial slots in the coupling head on the one hand,and between the central recess of the coupling disk and a projection onthe distributor shaft, on the other hand, is such that there is acardanic connection between the drive shaft and distributor shaft, withthe result that tolerance-related offsets between the drive shaft anddistributor shaft are compensated without difficulty.

If there are altogether four axial slots in the coupling head, which arein each case arranged offset at 90° to one another, and,correspondingly, four radial coupling webs on the coupling disk whichare arranged offset at 90° to one another, such a cardanic articulationof the distributor shaft on the drive shaft is achieved, according to anexpedient embodiment of the invention, in that two coupling websarranged diametrically to one another are seated in the associated axialslots without play in the circumferential direction and the recess inthe coupling disk has two flanks which extend parallel and at rightangles to the coupling webs seated without play in the axial slots andagainst which the projection on the distributor shaft bears without playby means of parallel spigot surfaces facing away from one another.

According to a further embodiment of the invention, the two remainingcoupling webs of the coupling disk which are located diametricallyopposite one another are seated with play in the circumferentialdirection in the associated axial slots in the coupling head. Thecircumferential play is appropriately adapted to tolerances (centeroffset) occurring.

According to an advantageous embodiment of the invention, the couplingdisk rests on the slot bottom of the axial slots and forms an axiallimiting wall for the roller shoes. As a result, the slot bottom doesnot have to be particularly plane for the roller shoes to bear on it, sothat the most cost-effective production process can be employed forproducing the axial slots. For example, these can be cut in by means ofa rotating parting or grinding wheel into the cylindrical wall of thecoupling head from its free end face, the grinding wheel being advancedincreasingly axially from the free end of the coupling head. The axialslots can each be cut in individually. However, if there is an evennumber of axial slots in the coupling head, two diametrically oppositeaxial slots can also in each case be cut in simultaneously in a singleoperation.

According to an expedient embodiment of the invention, the coupling diskperforms the function of limiting the torque in relation to thedistributor shaft. It forms a predetermined breaking point in the eventof a seizure of the distributor shaft, for which purpose the couplingdisk, by a choice of material or shaping, is designed in such a way thatthe radially projecting coupling webs break off when the permittedtorque maximum is exceeded.

According to a preferred embodiment of the invention, the mounting ofthe drive shaft in the pump casing is effected by a plain bearing bushnear the exit of the drive shaft from the pump casing and by a ballbearing between the coupling head and pump casing which is supportedboth radially and axially on the coupling head. This ensures an accurateshaft mounting in the axial and radial direction, this being of thegreatest importance, particularly in conjunction with a sensor forrecording the rotary-angle position of the drive shaft, for avoiding theinfluences of errors in the sensor output signal. The large bearingspacing between the two bearings means that only low bearing forces aregenerated in each bearing, with the result that the lifetime of thebearings is increased. The provision of the axial bearing does notnecessitate an increased axial overall length, since the bearing outerring is arranged in such a way that it covers the assembly clearance,necessary for the driving pin on the cam ring, inside the pump casing.

In a preferred embodiment of the invention, the coupling head has anaxial portion of reduced diameter on its free end face. There bears onthe annular shoulder, which forms at the transition to the end portionof reduced diameter, a thrust washer slipped onto the end portion. Theinner ring of the ball bearing is supported radially on the end portionof smaller diameter of the coupling head and axially on the thrustwasher and is retained in the axial direction by a retaining ring. As aresult of this constructive measure, the pressed-on inner ring of theball bearing stiffens the free ends of the claw-like wall segments ofthe coupling head which remain between the axial slots. The deformationof said wall segments in the radial direction, caused by thetransmission of the drive torque to the roller shoes, is therebysubstantially limited. The result of this is lower wear in the cammechanism on account of smaller inclinations of the roller shoes and animprovement in the injection-pressure trend on account of lowerelasticity.

DRAWING

The invention is explained in more detail in the following descriptionby means of an exemplary embodiment illustrated in the drawing. In this:

FIG. 1 shows a longitudinal section through a fuel-injection pump of thedistributor type with radial pistons for an internal-combustion engine,

FIG. 2 shows a section through the coupling head and cam ring along theline II--II in FIG. 1,

FIG. 3 shows a section along the line III--III in FIG. 1,

FIG. 4 shows a side view of a drive shaft of the fuel-injection pump inFIG. 1,

FIG. 5 shows a top view of a thrust washer seated on the coupling headof the drive shaft in FIG. 4,

FIG. 6 shows a top view of a coupling disk seated in the coupling headof the drive shaft in FIG. 4,

FIG. 7 shows a cross section through the coupling head of the driveshaft in FIG. 4, with a coupling disk seated in it, according to afurther exemplary embodiment,

FIGS. 8 and 9 each show diagrammatically a longitudinal section throughthe coupling head of the drive shaft in FIG. 4 to illustrate theproduction of the axial slots.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The fuel-injection pump of the distributor type, shown in longitudinalsection in FIG. 1, serves for supplying a plurality of, here fourinjection nozzles 29 of a diesel engine with fuel of predeterminedmetering which is under injection pressure. The fuel-injection pump hasa pump casing 10, into which a distributor body 11 is inserted from oneend face and a central bore 12 is made from the other end face, in whichcentral bore 12 a drive shaft 13 is held rotatably by means of a plainbearing bush 14 inserted into the bore 12. The distributor body 11limits, inside the pump casing 10, a pump inner space 15 filled withfuel which is maintained under feed pressure by a feed pump 16 seatedfixedly in terms of rotation on the drive shaft 13. Made in thedistributor body 11 coaxially relative to the drive shaft 13 is afurther bore 17, into which a guide bush 18 rotatably receiving thedistributor shaft 19 is inserted. The distributor shaft 19 is coupledfixedly in terms of rotation to the drive shaft 13, as is explained inmore detail below. The distributor shaft 19 carries four radial bores 20which are offset at identical circumferential angles to one another andin each of which a radial piston 21 is guided axially displaceably(FIGS. 1 and 3). The four radial pistons 21 limit with one end face acentral pump working space 22 and with their other end face bear, ineach case via a roller shoe 23 and a roller 24 rotatably held therein,on a cam track 25 which is formed on the inner face of a cam ring 26coaxially surrounding the drive shaft 13 and distributor shaft 19. Thepump working space 22 is connected via a distributor bore 27 to adistributor groove 28 which, during the rotation of the distributorshaft 19, successively connects the pump working space 22 to aninjection bore 30 leading to one of the injection nozzles 29. Theinjection operation is terminated by opening a solenoid valve 31 whichconnects a relief bore 32 leading to the distributor groove 28 andlocated in the distributor shaft 19 to the pump inner space 15. Theinjection pressure is generated by means of the lifting movement of theradial pistons 21 which is imparted to these, during the rotation of thedistributor shaft 19, by the cam track 25 on the cam ring 26, the radialpistons 21 bearing non-positively via the roller shoes 23 and rollers 24on this cam track 25 by means of the pressure in the pump working space22. To set the start of injection, the cam ring 26 can be rotated in aknown way in the circumferential direction within limits by an injectiontimer 33, the adjustment taking place in dependence on the fuel-feedpressure prevailing in the pump inner space 15.

For coupling the drive shaft 13 and distributor shaft 19, a stub-likecoupling head 34 engaging over the distributor shaft 19 in a cup-likemanner is formed at the end of the drive shaft 13 facing the distributorshaft 19 (FIGS. 1 and 4). Four axial slots 35 (see also FIG. 2) are madein the hollow-cylindrical wall of the coupling head 34 according to thenumber of radial bores 20 and radial pistons 21 and terminate freely onthe free end face of the coupling head 34. The axial slots 35 arearranged offset at the same circumferential angles as the radial bores20 to one another, that is to say here at 90°, and the assignment of thecoupling head 34 and distributor shaft 19 is such that the radial bores20 in the distributor shaft 19 are radially aligned with the axial slots35 in the coupling head 34. As shown diagrammatically in FIG. 8, theaxial slots 35 are made in a technically very simple way by a parting orgrinding wheel which is applied to the free end face of the couplinghead 34 and which is advanced increasingly axially. The wheelcircumference of the grinding wheel is indicated at 36 in FIG. 8. Twooperations are necessary in order to produce the altogether four axialslots 35 offset in each case at 90°, two diametrically opposite axialslots 35 being produced during each operation. The slot bottom of theaxial slots 35 is in the form of an arc of a circle.

Seated on the bottom of the axial slots 35 is a coupling disk 37 (FIGS.1, 2, 4 and 6) with four coupling webs 371-374 which project radially onthe disk circumference and are in one piece with the coupling disk 37and which are arranged offset at identical circumferential angles of 90°to one another. As becomes clear from FIG. 2, two diametral couplingwebs 371 and 373 are seated without play in the circumferentialdirection in the associated axial slots 35, whilst the other twocoupling webs 372 and 374 are provided with the play necessary for thetolerances occurring in the center offset between the drive shaft 13 anddistributor shaft 19, the axial slots 35 having the same width, that isto say are made narrower than the coupling webs 371, 373. The couplingdisk 37 carries centrally a central recess 38 which positively receivesan end projection 39 which projects coaxially on the end face of thedistributor shaft 19 (FIGS. 1 and 2). The recess 38 is dimensionedrectangularly, the two parallel longitudinal sides 381, 382 extending atright angles to those coupling webs 371, 373 which are seated withoutplay in their associated axial slots 35. The end projection 39 of thedistributor shaft 19 bears without play on these longitudinal sides 381,382 by means of parallel projection surfaces 391, 392 pointing away fromone another. This design of the coupling webs 371, 373 and of the recess38 achieves a supporting articulation of the distributor shaft 19 on thedrive shaft 13 which compensates a tolerance-related center offset ofthe drive shaft 13 and distributor shaft 19.

The coupling disk 37, in addition to the function of connecting thedrive shaft 13 and distributor shaft 19 fixedly in terms of rotation,also has the function of torque limitation. For this purpose, thecoupling disk 37 is designed in such a way that the radially projectingcoupling webs 371-374 break off when the predetermined torque maximum isexceeded. A piston seizure in the distributor shaft 19 therefore leadsto the breaking of the coupling disk 37 and consequently to theuncoupling of the drive shaft 13 and distributor shaft 19, so thatfurther destruction in the fuel-injection pump is prevented.

After the coupling disk 37 has been inserted into the coupling head 34,the roller shoes 23 together with rollers 24 rotatably mounted thereinare inserted into the axial slots 35. The coupling webs 371 - 374 of thecoupling disks 37 thus limit the guidance of the roller shoes 23 in theaxial slots 35 in the axial direction. On the axially opposite side, theguidance of the roller shoes 23 is limited by a thrust washer 40 (FIGS.1, 4 and 5) which is slipped onto the coupling head 34. The couplinghead 34 has an axial portion 341 of reduced diameter on its free endface. Pushed onto this axial portion 341 is the thrust washer 40 whichcomes to bear on an annular shoulder 342 of the coupling head 34, saidannular shoulder 342 forming at the transition to the axial portion 341of reduced diameter, and which engages into the axial slots 35 by meansof four tabs 401 offset at a circumferential angle of 90° to oneanother. The tabs 401 of the thrust washer 40 thus limit, together withthe coupling webs 371-374 of the coupling disk 37, the axial movement ofthe roller shoes 23 in the guide slots of the roller shoes 23, saidguide slots being formed by the axial slots 35.

For the improved mounting of the drive shaft 13 in the pump casing 10,by means of which mounting axial force components on the drive shaft 13can also be absorbed, there is provided a ball bearing 41 with an innerbearing ring 42 and outer bearing ring 43 and with balls 44 rollingbetween them. The inner bearing ring 42 is pressed onto the axialportion 341 of reduced diameter radially against the thrust washer 40and is retained by means of a retaining ring 45 which engages into anannular groove 46 in the axial portion 341. The outer bearing ring 43 ofthe ball bearing 41 is received with appropriate play in the pump casing10 and is braced axially with the distributor body 11 against a casingshoulder 101. The outer bearing ring 43 covers, together with thedistributor body 11, an axial assembly clearance 47 inside the pumpcasing 10. This assembly clearance 47 is necessary for assembling theone-part cam ring 26 which is coupled to the injection timer 33 by meansof a radially projecting driving pin 48.

The design of the coupling head 34 on the drive shaft 13 for thecoupling of the distributor shaft 19 is not restricted to the design ofan even number of axial slots 35, four in the present example. Thus, ifthere is an odd number of radial bores 20 and of radial pistons 21seated therein in the distributor shaft 19, an odd number of axial slots35 in the coupling head 34' can also be provided, in which case, onceagain, each axial slot 35' receives displaceably in the radial directionthe roller shoe 23 assigned to the radial piston 21 together with theroller 24 rotatably mounted therein. FIG. 7 shows a cross sectionthrough such a coupling head 34' having three axial slots 35', intowhich, once again, a coupling disk 37' projects by means ofcorrespondingly three coupling webs 371', 372' and 373'. In accordancewith the arrangement of the axial slot 35', the coupling web 372' is ata greater distance, measured as a circumferential angle, from thecoupling web 371' and the coupling web 373' than the two coupling webs371' and 373' are from one another. In contrast to the coupling web373', the coupling webs 371' and 372' have a convex widening 50, bymeans of which they are seated in the associated axial slot 35' withoutplay in the circumferential direction. In contrast, the coupling web373' has play in the circumferential direction within the associatedaxial slot 35'. The recess 38, once again made rectangular, is orientedin such a way that its two longitudinal sides 381 and 382 extend atright angles to the middle coupling web 372' which is at the greatestdistance from the other two coupling webs 371' and 373'. Thisconstructive design for an odd number of axial slots 35' in the couplinghead 34' likewise ensures an cardanic articulation of the distributorshaft 19 on the drive shaft 13. The production, simple in manufacturingterms, of the odd number of axial slots 35' in the hollow-cylindricalcoupling head 34' is sketched in FIG. 9. Each axial slot 35' is cutindividually into the hollow-cylindrical wall of the coupling head 34'by applying a parting or grinding wheel axially to the free end of thelatter. The wheel circumference of the parting wheel is indicated bydot-and-dash lines in FIG. 9 and is designated by 36.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A fuel injection pump of the distributor type for supplyinga plurality of injection nozzles (29) of internal-combustion engines,which comprises, a rotating drive shaft (13) mounted in a pump casing(10), a distributor shaft (19) which is coupled fixedly in terms ofrotation to the drive shaft (13) and which, during rotation,successively makes a connection between a pump working space (22)integrated in said pump and one of the injection nozzles (29), and withpump pistons (21) which are each seated axially displaceably in a radialbore (20) of the distributor shaft (19) and which by means of one endface, each pump piston limits the pump working space (22) and by meansof another end face of each of said pump pistons, via rollers (24) heldrotationally movably in roller shoes (23), bear non-positively on a camtrack (25) of a cam ring (26) coaxialy relative to the distributor shaft(19) and fixed in the pump casing (10), wherein a stub-like couplinghead (34) that engages the distributor shaft (19) in a cup like manneris formed at one end of the drive shaft (13) facing the distributorshaft (19), the rotationally fixed coupling between the drive shaft (13)and distributor shaft (19) takes place by means of a coupling disk (37;37') which is seated in axial slots (35; 35') in the coupling head (34;34') by means of radial coupling webs (371-374; 371'-373) that projectradially on the disk circumference in one piece with the coupling disk(37; 37') and which positively receives a projection end (39) on an endface of the distributor shaft (19) in a control recess (38), a positiveconnection between the radial coupling webs (371-374; 371'-373') of thecoupling disk (37; 37') and the axial slots (35' 35') in the couplinghead (34' 34'), on the one hand, and between the central recess (38) inthe coupling disk (37; 37') and the end projection (39) of thedistributor shaft (19), on the other hand, is such that there is asupporting articulation of the drive shaft (11) and distributor shaft(19), the coupling disk (37) has at least two radial coupling webs (371,372, 373, 374; 371' 372' 373') offset from one another, of which tworadial coupling webs form an angle greater than 90° with one another andrest without play in the axial slots (35); the recess (38) in thecoupling disk (37) has two parallel sides extending at right angles toat least one of the coupling webs that rest without play in the axialslots (35), on which the sides of the face-end projection (39) of thedistributor shaft (19) rests with projection faces parallel to oneanother, the length of said projection faces is greater than the faceend projections located perpendicular to said projection faces, saidlatter faces are spaced apart from corresponding boundaries of therecess (38), and the coupling lands that are not guided with play engagethe axial slots with lateral play, and wherein the two remainingcoupling webs (372, 374) of the coupling disk (37) which are locateddiametrically opposite one another are seated with play in thecircumferential direction in the associated axial slots (35) in thecoupling head (34).
 2. A fuel injection pump of the distributor type forsupplying a plurality of injection nozzles (29) of internal-combustionengines, which comprises, a rotating drive shaft (13) mounted in abearing bush (14) supported in a central bore (12) in a pump casing (10)near an exit of said drive shaft (13) from said pump housing, said driveshaft (13) is affected by a ball bearing (41) between a coupling head(34) and the pump casing (10) with said ball bearing supported radiallyand axially on the coupling head (34), a distributor shaft (19) iscoupled fixedly in terms of rotation to the drive shaft (13) and which,during rotation, successively makes a connection between a pump workingspace (22) integrated in said pump and one of the injection nozzles(29), and with pump pistons (21) which are each seated axiallydisplaceably in a radial bore (20) of the distributor shaft (19) andwhich by means of one end face, each pump piston limits the pump workingspace (22) and by means of another end face of each of said pumppistons, via rollers (24) held rotationally movably in roller shoes(23), bear non-positively on a cam track (25) of a cam ring (26)coaxialy relative to the distributor shaft (19) and fixed in the pumpcasing (10), said coupling head (34) engages the distributor shaft (19)in a cup like manner and is formed at one end of the drive shaft (13)facing the distributor shaft (19), wherein the coupling head (34) has anaxial portion (341) of reduced diameter on a free end face, wherein athrust washer (40) bears on an annular shoulder (342) formed at atransition to the axial portion of reduced diameter, and wherein aninner bearing ring (42) of the ball bearing (41) bears on the axialportion (341) of reduced diameter of the coupling head (34) and axiallyon the thrust washer (40).
 3. A fuel injection pump of the distributortype for supplying a plurality of injection nozzles ( 29 ) ofinternal-combustion engines, which comprises, a rotating drive shaft(13) mounted in a bearing bush (14) supported in a central bore (12) ina pump casing (10) near an exit of said drive shaft (13) from said pumphousing, said drive shaft (13) is affected by a ball bearing (41)between a coupling head (34) and the pump casing (10) with said ballbearing supported radially and axially on the coupling head (34), adistributor shaft (19) is coupled fixedly in terms of rotation to thedrive shaft (13) and which, during rotation, successively makes aconnection between a pump working space (22) integrated in said pump andone of the injection nozzles (29), and with pump._pistons (21) which areeach seated axially displaceably in a radial bore (20) of thedistributor shaft (19) and which by means of one end face, each pumppiston limits the pump working space (22) and by means of another endface of each of said pump pistons, via rollers (24) held rotationallymovably in roller shoes (23), bear non-positively on a cam track (25) ofa cam ring (26) coaxialy relative to the distributor shaft (19) andfixed in the pump casing (10), said coupling head (34) that engages thedistributor shaft (19) in a cup like manner and is formed at one end ofthe drive shaft (13) facing the distributor shaft (19), wherein an innerbearing ring (42) of the ball bearing (41) is pressed against a thrustwasher (40) onto an axial portion (341) of reduced diameter of thecoupling head (34) and is retained by means of a retaining ring (45)inserted in an annular groove (46) in an axial portion (341).
 4. A fuelinjection pump of the distributor type for supplying a plurality ofinjection nozzles (29) of internal-combustion engines, which comprises,a rotating drive shaft (13) mounted in a bearing bush (14) supported .ina central bore (12) in a pump casing (10) near an exit of said driveshaft (13) from said pump housing, said drive shaft (13) is affected bya ball bearing (41) between a coupling head (34) and the pump casing(10) with said ball bearing supported radially and axially on thecoupling head (34), a distributor shaft (19) is coupled fixedly in termsof rotation to the drive shaft (13) and which, during rotation,successively makes a connection between a pump working space (22)integrated in said pump and one of the injection nozzles (29), and withpump pistons (21) which are each seated axially displaceably in a radialbore (20) of the distributor shaft (19) and which by means of one endface, each pump piston limits the pump working space (22) and by meansof another end face of each of said pump pistons, via rollers (24) heldrotationally movably in roller shoes (23), bear non-positively on a camtrack (25) of a cam ring (26) coaxialy relative to the distributor shaft(19) and fixed in the pump casing (10), said coupling head (34) thatengages the distributor shaft (19) in a cup like manner and is formed atone end of the drive shaft (13) facing the distributor shaft (19)wherein an outer bearing ring (43) of the ball bearing (41) is supportedin an axial direction on a casing shoulder (101) in the pump casing (10)and is clamped against the casing shoulder (101) by a distributor body(11) inserted into the pump casing (10) on an end face and receives thedistributor shaft (19).
 5. The injection pump as claimed in claim 1,wherein altogether four axial slots (35) arranged offset in each case at90° to one another are arranged in the coupling head (34), wherein thecoupling disk (37) has four radial coupling webs (371, 374) which arearranged offset at 90° to one another and of which two radial couplingwebs (371, 373) arranged diametrically to one another are seated withoutplay in the axial slots (35), and wherein the recess (38) in thecoupling disk (37) has two flanks (381, 383) which extend parallel andat right angles to the radial coupling webs (371, 373) seated withoutplay in the axial slots (35) and on which the end projection (39) of thedistributor shaft (19) bears by means of parallel projecting surfaces(391, 392) pointing away from one another.
 6. The injection pump asclaimed in claim 1, wherein altogether three axial slots (35') areprovided in the coupling head (34') of the distributor shaft (19) andcorrespondingly three coupling webs (371'-373') are provided on thecoupling disk (37'), of which the coupling webs (371' 372' ) offset atthe larger circumferential angle to one another are seated, as a resultof a convex widening (50) of their web width., in the associated axialslots (35') without play in the circumferential direction and whereinthe recess (38) in the coupling disk (37') has two flanks (381, 382)which extend at right angles to the coupling web (372') located furthestfrom the other two coupling webs (371', 373') and on which the endprojection (39) of the distributor shaft (19) bears without play bymeans of parallel projecting surfaces (391, 392) pointing away from oneanother.
 7. The injection pump as claimed in claim 1, wherein thecoupling disk (37) rests on a slot bottom of the axial slots (35), andwherein the roller shoes (23) bear axially on the coupling disk (37). 8.The injection pump as claimed in claim 5, wherein the coupling disk (37)rests on a slot bottom of the axial slots (35), and wherein the rollershoes (23) bear axially on the coupling disk (37).
 9. The injection pumpas claimed in claim 6, wherein the coupling disk (37) rests on a slotbottom of the axial slots (35), and wherein the roller shoes (23) bearaxially on the coupling disk (37).
 10. The injection pump as claimed inclaim 1, wherein the coupling disk (37) transmits a maximum torque, insuch a way that the radially projecting coupling webs (371-374) breakoff when the torque maximum is exceeded.
 11. The injection pump asclaimed in claim 5, wherein the coupling disk (37) transmits a maximumtorque, in such a way that the radially projecting coupling webs(371-374) break off when the torque maximum is exceeded.
 12. Theinjection pump as claimed in claim 6, wherein the coupling disk (37)transmits a maximum torque, in such a way that the radially projectingcoupling webs (371-374) break off when the torque maximum is exceeded.13. The injection pump as claimed in claim 7, wherein the coupling disk(37) transmits a maximum torque, in such a way that the radiallyprojecting coupling webs (371-374) break off when the torque maximum isexceeded.
 14. The injection pump as claimed in claim 1, wherein themounting of the drive shaft (13) in the pump casing (10) is effected bya plain bearing bush (14) near an exit of the drive shaft (13) from thepump casing (10) and by a ball bearing (41) between the coupling head(34) and pump casing (10) which is supported radially and axially on thecoupling head (34).
 15. The injection pump as claimed in claim 2,wherein the inner bearing ring (42) of the ball bearing (41) is pressedagainst the thrust washer (40) onto the axial portion (341) of reduceddiameter of the coupling head (34) and is retained by means of aretaining ring (45) inserted in an annular groove (46) in the axialportion (341).
 16. The injection pump as claimed in claim 2, wherein anouter bearing ring (43) of the ball bearing (41) is supported in theaxial direction on a casing shoulder (101) in the pump casing (10) andis clamped against the casing shoulder (101) by a distributor body (11)inserted into the pump casing (10) on an end face and receives thedistributor shaft (19).
 17. The injection pump as claimed in claim 3,wherein an outer bearing ring (43) of the ball bearing (41) is supportedin the axial direction on a casing shoulder (101) in the pump casing(10) and is clamped against the casing shoulder (101) by a distributorbody (11) inserted into the pump casing (10) on an end face and receivesthe distributor shaft (19).
 18. The injection pump as claimed in claim4, wherein an outer bearing ring (43) of the ball bearing (41) issupported in the axial direction on a casing shoulder (101) in the pumpcasing (10) and is clamped against the casing shoulder (101) by adistributor body (11) inserted into the pump casing (10) on an end faceand receives the distributor shaft (19).